METHOD FOR REPELLING GAME AND DEVICE THEREFOR

Abstract: A method for repelling game comprises its exposure to an effective airborne amount of a dialkyl sulfide with from 3 to 14 carbon atoms, preferably of the general formula CnH2n+2S, n being 4-8. Also disclosed is a game repellent device comprising a closed dispensing container of polymer material containing a composition which, as game repellent agent, comprises at least one dialkyl sulfide of the composition described above, dissolved in a dispensation retarding agent, the polymer material forming the container being selected to permit diffusion of said dialkyl sulfide through the container walls. Also disclosed is a method for device manufacture and a device transport or storage package, a dispensing container for a game repellent composition and a game repellent barrier comprising a plurality of said devices.

Description: Title: Method for repelling game and device therefor FIELD OF THE INVENTION The present invention relates to a method for repelling game, an device useful in carrying out the method, and further relates to a method for the manufacture of said device, a transport or storage package for said device, a dispensing container for a game repellent composition and a barrier for preventing access of migrating game to a road or exluding it from an area to be protected. BACKGROUND During the second half of this century the stock of game has increased substantially in many countries, in Sweden particularly the stock of elk and deer. This has led to problems of various kind, particularly in regard of road traffic and forest management. Some people are killed and many more hurt in accidents caused by game, including accidents caused by reindeer. In this application the term "game" as such and in combination with other words also relates to reindeer, cariboo and other only partially domesticated artiodactyles species. In forest management regrowth is impeded by small plants, particularly pine and spruce, constituting an important food source for elk and deer during the winter season. The resulting damage in this country amounts to several 100 illon Swedish kronor. Damage caused by game can, on the one hand, be contained by increased hunting and, on the other hand, by physically protecting roads and forest plantations. These measures, however, are not sufficient to reduce such damage to an acceptable level, the reason being that the species causing the damage also are valuable game. Only moderate reduction of game stock seems to be acceptable to hunting interests. Another reason is that various types of fences and other physical barriers have been shown to be expensive and, in many cases, insufficient. Experiments have also been carried out to keep out game from certain areas to be protected, or at least to reduce the frequence of ingression, in other ways than by physical exclusion, for instance, by optically effective means, such as game mirrors, which affect game psychologically. The potential use of odorous matter for such purpose has been known for a long time but implementation has been scarce. Coagulated blood powder giving off certain odorous compounds has been shown to have deterring effect on hare and rabbit, and has been used at a small scale for keeping these animals away from gardens and other delicate plantations. Various methods for protecting plants from being eaten by herbivores, particularly artiodactyles, have been disclosed, for example by spraying plants with a solution of strongly smelling fragrant oils in isopropanol. This however protects only the treated plant which is provided with a smell that is only disagreable but does not deter. Odorous compounds excreted by predators or by their urine and excrements have been shown to possess deterrent effect on artiodactyles species. Particularly wolf urine has been shown to be effective, even on game stock which for generations had not been in contact with wolves. The reason for this seems to be genetically determined. Some promising experiments have been made with paper or textile strips impregnated with wolf urine which is, however, expensive to procure, particularly in amounts needed for industrial applications. This seems to have prevented broader practical use of that method. Urine from predators which they also use for marking their territory has a very complex composition in respect of volatiles and comprises hundreds of compounds detectable by gas chromatography. Wolf urine, for instance, contains certain odorous components that also are excreted by other animals than carnivores, and even by plants or that are formed in microbial degradation of organic material, and which thus are not threatening to the game species one intends to affect. Single components in wolf urine thus are not suited per se as odorous repellants for game. In certain cases they even might attract game. Use of various constituents of wolf urine might alsoe be hindered by their low activity or short duration of effect because of high volatility or chemical instability, difficulties in their preparation, etc. The implicit teaching of prior art seems to be that that potential game deterring or repelling constituents in wolf urine are only effective in combination with others. As components in urine from wolf (canis lupus; Raymer, J. et al., Experientia 40 (1984) 707-719) coyote and dog are known, for instance, various dialkyl sulfides. However, dialkyl sulfides are not specific for urine from canine species but of wide occurrence in nature, for example in crude oil and in microbial degradation of proteins, and should therefore not be considered as species-specific pheromones (and thus potential game repellants) . Dialkyl sulfides and a wide array of other low-molecular weight compounds have been used to repel bees from growing crops treated with insecticides (DE-A- 4 012 224) and for extermination of insects (DE-C- 363 656) . Dimethyl sulfide is known as a minute component in a game repellent composition of highly complex nature (EP-A- 280 443) . OBJECTS OF THE INVENTION It is a primary object of the present invention to disclose volatile agents that elicit a distinct alarm and escape reaction in game pertaining to the artiodactyles, including species that are only partially domesticated, particularly species found in the temperate and subarctic zones of the northern hemisphere, and which are useful as game repellent agents. Because of the required stability for extended time periods and its use outdoors, the repellant should have low toxicity and cause essentially no environmental harm; this should also hold true for adjuvants and devices for transport and dispensation of the repellant. It is an object of the present invention to disclose a method of repelling game which, in comparison with known methods, is effective, low-cost, and which allows keeping out game under a long period of time from areas to be protected. It is another object of the present invention to disclose a device useful for carrying out the method. It is a further object of the present invention to disclose a barrier for exclusion of migrating game from roads and areas to be protected and the like. It is an additional object of the invention to disclose a method of manufacture of the device according to the invention. It is also an object of the invention to disclose a transport and/or storage package for one or several devices according to the invention. It is an additional object of the invention to disclose a dispensation container for game repellants. SUMMARY OF THE INVENTION In accordance with the present invention, the method for repelling game comprises exposing game to an effective airborne amount of a dialkyl sulfide with from 3 to 14 carbon atoms. It is preferred for the dialkyl sulfide to have the general formula C n H 2n+2 S, n being 4 - 8. It is also preferred for the dialkyl sulfide to be selected from the group consisting of diethyl sulfide, dipropyl sulfide, dibutyl sulfide, methyl propyl sulfide, butyl methyl sulfide, methyl pentyl sulfide, ethyl propyl sulfide, and butyl etyl sulfide. Most preferred is butyl methyl sulfide. These alkyl sulfides are effective in very small airborne amounts, have low toxicity and can be easily and economically prepared from low-cost starting materials. They are easily biodegradable and environmentally harmless in the concentrations used. In accordance with the present invention, the device useful for carrying out the method according to the invention comprises a closed dispensing container of polymer material containing a composition which, as game repellent agent, comprises at least one dialkyl sulfide having from three to fourteen carbon atoms dissolved in a dispensation retarding agent, the polymer material forming the container, preferably polyethylene or polypropylene, being selected to permit diffusion of said dialkyl sulfide through the container walls. A purpose with the dispensation retarding agent is to control and reduce the amount of game repellent agent diffusing through a given container wall area per time unit; the dispensation retarding agent, which can comprise more than one constituent, should have a low boiling pressure, preferably equal or lower than that of the game repellent agent, and its diffusion rate through the walls of the container should preferably be substantially smaller than that of the game repellent agent. It is also preferred for the dispensation retarding agent to have higher polarity than the game repellent agent. Another purpose with the dispensation retarding agent of low toxicity and low vapour pressure is to facilitate manipulation of the game repellent agent during filling of dispensing containers. A further purpose with the dispensation retarding agent is to protect the game repellent agent against oxidation and to act as solvent for adjuvants. The device useful for carrying out the method according to the invention is a closed container essentially consisting of a polymer material permitting slow diffusion of the game repellent agent through the container walls. These semipermeable walls, in combination with the dispensation retarding agent, thus provide for continuous slow dispensation of the game repellent agent to the ambient atmosphere. Once the game repellent agent has become airborne it will be spread by circulating air and exhibit its game repellent effect. A game repellent concentration gradient will be established around the device. In the vicinity of the device the airborne concentrations of game repellent agent will be high enough to repel game, i.e. to make game to move in a direction away from the device. At a greater distance from the device, the airborne concentrations of repellent agent will fall below the detection threshold for the individual animal, and therefore will no longer affect its behaviour. It has been found that certain low polarity polymers (polymers formed from low polarity monomers) , such as linear low density polyethylene, are particularly suited as polymer material for the device according to the invention. It is preferred for the at least one dialkyl sulfide in the container to have the general formula C n H 2n+2 S, n being 4 - 8; more preferred is that it be selected from the group consisting of diethyl sulfide, dipropyl sulfide, dibutyl sulfide, methyl propyl sulfide, butyl methyl sulfide, methyl pentyl sulfide, ethyl propyl sulfide, and butyl etyl sulfide. Most preferred is butyl methyl sulfide. According to a preferred aspect of the invention, the dispensation retarding agent contains at least 25 % by weight of an agent selected from the group consisting of C 5 -C- 24 saturated and unsaturated fatty acids, C 5 -C 24 saturated fatty alcohols, polyethylene glycol and polypropylene glycol having a molecular weight of about 200 to 600, and mixtures thereof. According to another preferred aspect of the invention, said composition comprises one or several additives selected from the group consisting of anti-oxidants, for example radical capturing and/or metal complex forming agents, light absorbants, particularly UV-absorbing agents, pH-stabilizing agents, surfactants, consistency- providing agents, and bulk agents insoluble in the composition, therein also being comprised agents that swell in contact with the composition. According to a further preferred aspect of the invention, the permeability of the container walls is selected to provide for dispensation of effective amounts of repellent agent down to temperatures of - 10° C. Particularly preferred is a container made of a polymer material, such as linear low density polyethylene, that at a temperature of 4° C and a wall thickness of 1 mm permits diffusion of between 0,05 and 2,5 mg game repellent agent per day and cm 2 wall area. In accordance with the present invention the method for manufacture of the game repellent device according to the invention comprises segmentation of a plastic tube to obtain a tube segment, radial compression of the tube segment at its one end to form a bottom and a lug while adding heat or energy, partial filling of the tube segment with a predetermined volume of a liquid composition containing a volatile game repellent agent, such as a dialkyl sulfide having from three to fourteen carbon atoms, dissolved in a dispensation retarding agent, sealing the open other end by radial compression while adding heat or energy to form a lock and another lug, and providing, at one or both of the lugs, means for attachment of the game repellent device to trees, poles, etc. In accordance with the present invention is disclosed a transport and/or storage package for one or several dispensing devices according to the invention, the packaging material of which comprises a thin walled laminate comprising at least one gas-impermeable layer. In accordance with the present invention is also disclosed a barrier against migrating game based on the method and/or the device according to the invention. The barrier comprises a plurality of devices according to the invention in an interspaced relationship. The distance between neighbouring devices is determined by the game repellent agent concentration gradient and scent detection threshold of the animals to be kept out. The devices are intended to be attached to trees, bushes, poles, or similar at a height of from about 0,5 to about 2,5 m above the ground. A game barrier according to the invention extending substantially in one direction will comprise a plurality of devices according to the invention arranged along a straight or curved line. Preferred is a distance of between 2 and 25 m between neighbouring devices which are attached to trees, etc. in the way described above. In accordance with the present invention is furthermore disclosed a dispensing container for a game repellent composition comprising a volatile game repellent agent of low polarity (hydrocarbon, ether, thioether or similar) diffusable through polymer material dissolved in a dispensation retarding agent, said container comprising a closed chamber having walls of polymer material, preferably linear low density polyetylene or polypropylene, arranged for enclosure of said game repellent composition and permitting, at temperatures down to about -10° C, diffusion of from 0,05 to 2,5 mg repellent agent per day and cm 2 at a wall thickness of 1 mm. This dispensing container should also be useful for dispensing low polarity game repellants other than those disclosed according to the present invention. Further objects and advantages of the invention are apparent from the description of preferred embodiments and the appended claims. BRIEF DESCRIPTION OF THE DRAWING The invention will now be explained in greater detail with reference to various non-limiting preferred embodiments illustrated in part in an appended drawing which shows Fig. 1 a game repellent device according to the invention, in a side view and in a longitudinal axial section perpendicular to the lugs (line B - B in Fig. 2) , Fig. 2 the device of Fig. 1, in a side view and in a longitudinal axial section parallel to the lugs (line A - A in Fig. 1) , Fig. 3 a cartographic sketch type top view of a game barrier according to the invention comprising a plurality of game repellent dispensing devices, and Fig. 4 a cartographic sketch type top view of a game barrier according to the invention similar to that shown in Fig. 3, but with the game repellent dispensing devices in a zig-zag relationship. DETAILED DESCRIPTION Example 1 Dispensing container The dispensing container or capsule 1 shown in Figs. 1 and 2 is about 5 cm long and has upper and lower terminal lugs 2, 3 and an integral container portion 4 extending between these lugs and having a wall 5 thickness of 1 mm and a lumen of 8 mm. The capsule material is low density polyethylene. The lower part of container portion 4 is filled with a composition 6 containing game repellant. The free volume above composition 6 is filled with air. The upper lug 2 has a through hole 8 for attachment purposes. The liquid composition 6 in the container portion 4 is a 1 : 1 (v/v) mixture of butyl methyl sulfide (repellant) and a fatty acid fraction derived from tall oil (dispensation retarding agent) with the trade name Bevacid™ 2 (Bergvik Kemi AB, Sandarne, Sweden) described to contain 30 % by weight of oleic acid and 64 % by weight of multiple unsaturated fatty acids of which about 90 % by weight are non-conjugated. Benzyl alcohol and 1-hexanol have also been found to be particularly useful dispensation retarding agents. Butyl methyl sulfide and the other sulfides disclosed are prior known compounds and can be easily prepared by standard methods, e.g. methods referenced in Beilstein and other standard reference literature. Example 2 Manufacture and packaging of the dispensing device The dispensing device described in example 1 is manufactured in the following way. A tube of LD- polyethylene is cut into pieces about 60 mm in length, which are closed at the bottom by radial compression under heating, are arranged in an upright position and filled with 1,4 ml of a 1 : 1 (v/v) mixture of game repellent agent and the tall oil fraction according to example 1. The upper end of the container is then heat sealed and a hole punched into the resulting lug. A number of the dispensing containers thus obtained is packed into an outer envelope of gas tight laminate foil of type PET/A1/PE (polyethylene terephthalate/aluminium/ polyetylene) . The capsules 1 can be stored and transported without their odour causing inconvenience. The outer envelope is removed only when mounting the capsules to form a game repellent barrier. Instead of the tube segment with one bottom closed as described above a injection moulded container of about the same general form and size which may lack the bottom lug can be used for filling with the composition according to the invention and be further processed as described above. Sealing of the container with ultrasound was found to be particularly useful. Example 3 Mounting of the dispensing devices The map sketch in Fig. 3 shows the mounting location of a number of dispensing capsules 1 along a road 12 (which is intended to be protected from game intending to pass over from one side to the other) by means of poles 10 anchored in the ground and at trees 11. The barrier thereby obtained (indicated by S - S, broken line) bars game from reaching the road 12 in an area extending along the road and parallel with the barrier. When setting up the barrier one should consider the influence of (predominant) wind direction(s) on air transport of the game repellent agent dispensed by the containers. When the wind blows in a direction against the "backside" of the barrier, i.e. the side facing away from game approaching the road (arrow V) , such as indicated by arrow M in Figs. 3 and 4, the game will scent the agent before reaching the barrier and turn back. When the wind is blowing essentially in the opposite direction, such as indicated by arrow R in Fig. 3, the game will scent the repellent agent only in the immediate vicinity of the barrier, and sometimes only when it already has penetrated the barrier, i.e. the dashed line S - S between two neighbouring dispensing capsules 1, but will immediately turn back and run in the direction where it came from. For this reason scent barriers like the one according to the invention should not be arranged immediately adjacent to the road 12 or the area intended for protection, but at a distance D from the road or said area, where D is suitably at least three times the average distance E between neighbouring dispensing containers 1. In order to increase the game repellent effect in a situation where the main wind direction R is about the same as the direction V of game approaching the barrier, the latter (S' - S') can be given the zig-zag arrangement shown in Fig. 4; the respective dispensing containers are designated 1' , the distance between neighbouring containers 1' is designated by E', and the average distance between the road 12 and the barrier S' - S' by D'. The zig-zag relationship of the containers 1' provides for greater protection against unintended passage of game through the barrier should the wind direction coincide with the direction of game approaching the barrier. The above described distance relationships should equally apply to scent barriers in general and thus not be confined to implementation solely by the game repellent devices according to the present invention. Example 4 Repelling experiments with deer and elk A barrier consisting of unmarked containers filled with butyl methyl sulfide and a tall oil fraction according to example 2 was set up in forest terrain in Vasternorrland (northern Sweden) . The containers were fixed at trees or similar at an average height of 1.5 m above the ground and at an average distance of 15 m between each other. It was observed that artiodactyles game, primarily elk, approaching the barrier would stop near the barrier and proceed in parallel with it or turn back. In separate experiments it was found that noticeable effect extended over a period of more than six months. No effect was observed in an experiment with containers filled with tall oil fraction only. Small scale repelling experiments using dietyl sulfide, dipropyl sulfide, dibutyl sulfide, methyl propyl sulfide, methyl pentyl sulfide, etyl propyl sulfide and butyl ethyl sulfide also showed effect which however was inferior to that of butyl methyl sulfide.

Claims: C l a i m s 1. A method for repelling game comprising exposing game to an effective airborne amount of a dialkyl sulfide with from 3 to 14 carbon atoms. 2. The method according to claim 1, wherein the dialkyl sulfide has the general formula C n H 2n+2 S, n being 4 - 8. 3. The method according to claim 2, wherein the dialkyl sulfide is selected from the group consisting of diethyl sulfide, dipropyl sulfide, dibutyl sulfide, methyl propyl sulfide, butyl methyl sulfide, methyl pentyl sulfide, ethyl propyl sulfide, and butyl etyl sulfide. 4. The method according to claim 3, wherein the dialkylsulfide is butyl methyl sulfide. 5. A game repellent device comprising a closed dispensing container of polymer material containing a composition which, as game repellent agent, comprises at least one dialkyl sulfide having from three to fourteen carbon atoms dissolved in a dispensation retarding agent, the polymer material forming the container, preferably polyethylene or polypropylene, being selected to permit diffusion of said dialkyl sulfide through the container walls. 6. The game repellent device of claim 5, wherein said dialkyl sulfide has the general formula C n H 2n+2 S, n being 4 - 8 7. The game repellent device of claim 6, wherein said dialkyl sulfide is selected from the group consisting of diethyl sulfide, dipropyl sulfide, dibutyl sulfide, methyl propyl sulfide, butyl methyl sulfide, methyl pentyl sulfide, ethyl propyl sulfide, and butyl etyl sulfide. 8. The game repellent device of claim 5, wherein the dispensation retarding agent contains at least 25 % by weight of an agent selected from the group consisting of C 5 -C- 24 saturated and unsaturated fatty acids, C 5 -C 24 saturated fatty alcohols, polyethylene glycol and polypropylene glycol having a molecular weight of about 200 to 600, and mixtures thereof. 9. The game repellent device of claim 5, wherein said composition comprises one or several additives selected from the group consisting of anti-oxidants, for example radical capturing and/or metal complex forming agents, light absorbants, particularly UV-absorbing agents, pH- stabilizing agents, surfactants, consistency providing agents, and bulk agents insoluble in the composition, therein also being comprised agents that swell in contact with the composition. 10. The game repellent device of claim 5, wherein the permeability of the container walls is selected to provide for dispensation of effective amounts of repellent agent down to temperatures of - 10° C. 11. A method for manufacture of the game repellent device according to any of claims 5 to 10, comprising segmentation of a plastic tube to obtain a tube segment, radial compression of the tube segment at its one end to form a bottom and a lug while adding heat or energy or, alternatively, injection moulding of an about tubular container with one open end, partial filling of the tube segment or container with a predetermined volume of a liquid composition containing a volatile game repellent agent, such as a dialkyl sulfide having from three to fourteen carbon atoms, dissolved in a dispensation retarding agent, sealing the open other end, preferably by radial compression, while adding heat or energy to form a lock and, preferably, another lug, and providing, at one or both of the lugs, means for attachment of the game repellent device to trees, poles, etc. 12. A transport and/or storage package for one or several dispensing devices according any of claims 5 to 10, the packaging material of which comprises a thin walled laminate comprising at least one gas impermeable layer. 13. A barrier preventing access of migrating game to a road or excluding it from an area to be protected, comprising a plurality of devices according to any of claims 5 to 10 in interspaced relationship in the proximity of said road or of said area. 14. The barrier of claim 13, wherein the distance between neighbouring devices is from about 2 m to about 25 m and the average distance between the barrier and the road or area to be protected is at least three times the average distance between neighbouring devices. 15. A dispensing container for a game repellent composition comprising a low polarity volatile game repellent agent, such as a hydrocarbon, an ether, a thioether or a compound of similar polarity, diffusable through polymer material dissolved in a dispensation retarding agent, said container comprising a closed chamber having walls of polymer material, preferably linear low density polyetylene or polypropylene, arranged for enclosure of said game repellant composition and permitting, at temperatures down to about -10° C, diffusion of from 0,05 to 2,5 mg repellent agent per day and cm 2 at a wall thickness of 1 mm.

Inventors: JOHANSSON GERHARD, JOHANSSON, GERHARD
Applicants: JOHANSSON GERHARD, JOHANSSON, GERHARD
Application year: 1994
Main classification: A01N31
IPC codes: A01N25, A01N31